1. Field of the Invention
The present invention relates to a conveyance apparatus which allows a workpiece supported by a conveyor to pass through a plurality of treating processes while changing its position, and more particularly to a conveyance apparatus which is suitable for a surface treatment line such as a car body painting line in vehicle manufacture. Further, the present invention relates to a conveyance path connecting a pretreatment process and a drying process, used, for example, for painting parts of a vehicle.
2. Description of the Prior Art
In a painting line for a vehicle, there are many treating processes such as pretreatment, electrodeposition, washing, painting, and drying and a workpiece is transferred among these treating processes by a conveyor. When painting of a comparatively large body of, for example, a four-wheel car is required by dipping, as shown in FIG. 17A, a workpiece W which has been transferred on a floor conveyor FC located on a floor is transferred to an overhead conveyor HC for hanging support. The overhead conveyor HC is enabled to move up and down in a vertical manner relative to the pretreatment and electrodeposition line. In such a condition, the workpiece W is moved vertically for dipping treatment while passing above pretreatment and electrodeposition baths and the like and then transferred again to the floor conveyor FC.
Also, in the case of electrodeposition, to obtain fine painting quality, it is known that the workpiece is rotated in an electrodeposition paint bath to change its position to a successive variety of positions (e.g. see Japanese Patent Publication No. Hei 6-104920 and Japanese Unexamined Patent Publication No. Hei 2-111481).
On the other hand, when painting of a comparatively small body of a two-wheel vehicle is required, as shown in FIG. 17B, it is possible to perform all painting processes using the overhead conveyor HC. Accordingly, it is not necessary to transfer the body in the middle of the painting line as with the four-wheeled vehicle. However, as far as the dipping treatment is concerned, the vertical operation is conducted in the same manner as shown above.
In the following description, a workpiece position of a type in which the workpiece is mounted and supported on a floor conveyor is called a floor conveyor position, a workpiece position of a type in which the workpiece is hung and supported is called an overhead conveyor position, and a workpiece position of a type in which the workpiece is substantially supported in a level plane at the side of the conveyor is called a side conveyor position. Further, rotation in a plane parallel to and perpendicular to the direction of travel is called vertical rotation, while rotation in a plane at right angles to the direction of travel is called horizontal rotation.
Also, for example, in the manufacture of a fuel tank, body frame or the like as parts for a motorcycle, when the tank or the frame which undergoes electrodeposition painting and the tank or frame which does not undergo electrodeposition painting are transferred on a common line, as shown in FIG. 23, a diverging point is provided in a line at the upstream side of an electrodeposition bath and a line A is used for the workpiece being painted, whereas a by-pass line B is used for the workpiece not being painted and these lines join in the junction at the downstream side of the electrodeposition bath.
Further, in the case of, for example, painting parts or the like of a vehicle, as shown in FIG. 27, for example, after a workpiece W conveyed by means of a carrier G along a workpiece conveyance path H has been immersed in an electrodeposition bath (not shown) at a pretreatment process A, the workpiece W after being removed from the electrodeposition bath is transferred to a drying process C to dry a paint film. At this time, in order to prevent hot air from the drying process C from entering the pretreatment process A, a hot air isolating zone B is generally provided between the pretreatment process A and the drying process C. The hot air isolating zone B is shortened to save a space by having an equipment formed in such a construction that, a workpeice conveying path H of the hot air isolating zone B slants, and a workpiece conveying path H of the drying process C is located at a higher position, thereby making it difficult for the hot air from the drying process C to enter the pretreatment process A.
In a process wherein the workpiece position must be changed to the floor conveyor position and the overhead conveyor position, if the workpiece has to be transferred from one conveyor to another whenever the workpiece position is changed, loss of time is caused. It is therefore desired not to transfer the workpiece while being conveyed at least in one continuous process even though the workpiece position is changed.
Further, in a method such as a dipping treatment wherein a conveyance line is continuously changed vertically, the proportion of time not suitable for dipping but required only for moving the workpiece in and out of a bath becomes large relative to the substantial dipping time of the workpiece. Accordingly, it is also desired to improve this loss of time. Also, in the case of the overhead conveyor, there is some possibility that the painting quality deteriorates when dust or the like falling from the overhead conveyor adheres to the workpiece. It is therefore desired to realize a conveyance method which keeps such falling substances from adhering to the workpiece. It is therefore a first object of the present invention to solve the above-mentioned disadvantages.
Also, if the above-mentioned by-pass line B is installed, there are disadvantages that the equipment construction including the conveyance apparatus is large in size, and the equipment cost is high, and conveying control becomes complicated.
It is therefore a second object of the present invention to solve the above-mentioned disadvantages.
Furthermore, the hot air isolating zone B having the slanting conveying path as mentioned above is still too long, therefore, it is preferable to further shorten the zone B.
It is therefore a third object of the present invention to minimize the distance between a pretreatment process and a drying process and to reduce the equipment space further, in a conveyance apparatus in which difference in height is provided for a workpiece conveyance path for the pretreatment process and a workpiece conveyance path for the drying process.
To solve the above-noted disadvantages, according to the first invention, a conveyance apparatus has a conveyor for supporting a workpiece and is adapted to allow the workpiece to pass through a plurality of treating processes while changing a workpiece position, wherein a position control mechanism for changing the workpiece position is provided so that the workpiece position required for each treating process can be continuously changed without transfer of the workpiece.
According to the present invention, the workpiece is conveyed to a plurality of treating processes which require different workpiece positions while being supported by the same conveyor and the position control mechanism is provided to allow the workpiece to be changed to the most suitable workpiece position for each process. Thus, it is no longer necessary to transfer the workpiece to another type of conveyor for each process and continuous conveyance is possible. It is therefore possible to reduce the number of transfer processes that have been required for the conventional conveyance apparatus and improve the efficiency for conveyance of the workpiece among the plurality of processes.
This position control mechanism can be arranged to either control the workpiece position to provide a floor conveyor position in which the workpiece is supported above the conveyor and an overhead conveyor position in which the workpiece is hung and supported below the conveyor; or to allow the workpiece to be supported substantially in a level plane on the side of the conveyor to realize a side conveyor position; or to continuously control the workpiece position to provide the floor conveyor position, the overhead conveyor position and the side conveyor position. The position control mechanism can also be arranged to realize all of the above positions.
Also, since the floor conveyor position and the overhead conveyor position are controllable, continuous treatment can be carried out without transfer of the workpiece even in such a treating process as the dipping treatment where the floor conveyor position and the overhead position are alternately required. If the system is controlled to provide the side conveyor position, the workpiece can be supported substantially in a level plane laterally from the conveyor. It is therefore effective in such a process, in particular a painting process, to prevent substances falling from the conveyor from adhering to the workpiece. Furthermore, if the floor conveyor position, the overhead conveyor position, and the side conveyor position are controlled in combination, it is possible to easily realize such complicated position control where the workpiece is required to rotate to allow each surface to face a specified direction in sequence.
The position control mechanism also makes it possible for the workpiece position to be changed either to provide vertical rotation within a plane parallel to the direction of travel of the conveyor or to provide horizontal rotation that rocks within a plane perpendicular to the direction of travel, or makes both vertical and horizontal rotation possible simultaneously.
This kind of control between the floor conveyor position and the overhead conveyor position can be realized by rotating the workpiece vertically. It is suitable for a continuous conveyance method that controls the workpiece position while continuously conveying the workpiece. In this case, if the rotational shaft projecting laterally from the conveyor is arranged to support the workpiece and rotated around its axis, the workpiece can be vertically rotated.
Also, control between the floor conveyor position and the overhead conveyor position and if necessary, control among the workpiece positions including the side conveyor position can be realized by rotating the workpiece horizontally. In this case, control can be easily realized by rocking the arm member within a plane where the horizontal rotation is made or by rotating a moveable portion provided on a part of the conveyor together with the workpiece. It is especially suitable for a tact conveyance method that intermittently conveys the workpiece.
Moreover, the conveyance apparatus is characterized in that a part of the conveyor is arranged to serve as a moveable portion and a rotational means is provided to rotate the moveable portion in a plane at right angles to the direction of travel of the conveyor, wherein the rotational means rotates the moveable portion together with the carrier.
According to the present invention, a part of the conveyor is provided with a moveable portion and when the moveable portion is rotated by a rotational means, not only the moveable portion, but also a carrier that is supported by the moveable portion rotates integrally. It is therefore possible to rotate a workpiece horizontally so as to change its position freely to a floor conveyor position, an overhead conveyor position and the like. Thus, it is no longer necessary to transfer the workpiece even when the workpiece position must be changed for every continuous process, therefore loss of time can be reduced. Accordingly, it is particularly suitable for a tact treatment where conveyance is intermittently stopped at every process for a necessary treatment.
In this case, the carrier can move like a monorail on the periphery of the conveyor that passes through the center portion of the carrier. Also, a carrier feeding means for moving the carrier on the conveyor in the direction of travel is provided parallel to the conveyor and the carrier can be provided with a flange portion which always engages the carrier feeding means.
If the carrier is supported like a monorail on the conveyor, the supporting construction of the carrier is simplified and strengthened. Thus, conveyance of the workpiece can be stabilized and it is especially favorable when a heavy workpiece must be supported. In addition, if the carrier is provided with a flange which engages a carrier feeding means provided parallel to the conveyor, the carrier is always maintained in the engaging condition with the carrier feeding means even if the carrier rotates and movement of the carrier is enabled. On the other hand, in a method where the carrier is supported on one side of the conveyor, since the workpiece can be supported laterally away from the conveyor, thereby keeping substances falling from the conveyor from adhering to the workpiece.
Further, it is possible to convey the carrier in the direction of travel while supporting it on one side of the conveyor. The rotational means may be a step motor that can be situated within the conveyor.
Also, since a part of the conveyor is arranged to serve as the moveable portion, it is possible to strengthen the moveable portion and simplify the construction comparatively. The rotational means can be easily formed with a step motor and the like. When the step motor is used, it can be easily housed inside a hollow portion of the conveyor, and the rotational direction and angle are controllable.
In the second invention, a conveyance apparatus is provided for mixed workpieces in which a workpiece conveying path is provided above a treatment bath, and a workpiece to be immersed in the treatment bath and a workpiece not to be immersed in the treatment bath are adapted to be mixedly conveyed by means of a carrier which is capable of running along a travelling rail of said workpiece conveying path, characterized in that a carrier inversion mechanism is provided in at least one portion of said workpiece conveying path above said treatment bath, and said workpiece to be immersed in said treatment bath is inverted in a plane at right angles to said conveying path by said carrier inversion mechanism to allow the workpiece to pass said treatment bath.
When the workpiece is transferred toward the treatment bath, the workpiece which is not be immersed in the treatment bath is allowed to travel in a condition in which the travelling course of the workpiece passes above the treatment bath, whereas the workpiece which is to be immersed in the treatment bath is converted to a position in which the travelling course of the workpiece passes inside the treatment bath.
The carrier inversion mechanism is so designed that the transporting course of the workpiece is changed vertically by inverting the workpiece together with the carrier by 180xc2x0. For example, a center of an inversion axis is set to be spaced to a certain extent from the workpiece.
Also, the treatment bath can be applied, for example, to a dipping bath for electrodeposition painting, a dipping bath for paint pretreatment, and other dipping baths.
Further, the carrier inversion mechanism is enabled to be inverted together with the travelling rail of the workpiece conveying path.
Since the carrier inversion mechanism is enabled to be inverted together with the travelling rail of the workpiece conveying path, it is possible to simplify the inversion mechanism for the workpiece which is supported by the carrier.
Furthermore, the carrier inversion mechanism is paired to position an intermediate travelling portion between the upstream side and the downstream side of the workpiece conveying path above the treatment bath.
In this manner, since a pair of carrier inversion mechanism is provided on both the upstream and downstream sides and the intermediate travelling portion is also provided therebetween, it is possible to secure sufficient immersion time for the workpiece and satisfactory immersion treatment can be performed.
Also, the travelling rail is formed as a double, upper and lower rail, structure.
Therefore, because the travelling rail has this double, upper and lower rail, structure, for example, in both cases where the workpiece not immersed in the treatment bath is moved while being supported above the carrier, and where the workpiece immersed in the treatment bath is moved while being supported below the carrier, it is possible to prevent interference between a conveying stand installed on the floor surface and the carrier.
When the intermediate travelling portion is provided and both the immersed workpiece and the non-immersed workpiece are caused to pass this intermediate travelling portion, for example, the conveying stand is positioned between the upper and lower rails. If the workpiece is supported above the carrier, the carrier is caused to move along the upper rail. If the workpiece is supported below the carrier, the carrier is caused to move along the lower rail. Thus, there is no interference between the conveying stand and the carrier.
According to the third invention, a conveyance apparatus is provided in which different heights are provided for a workpiece conveyance path for a pretreatment process and a workpiece conveying path for a drying process, a connecting workpiece conveyance path being provided at an intermediate portion of the two processes, characterized in that on said connecting workpiece conveyance path, a conveyance path lifter mechanism is provided to transfer a workpiece conveyance from the workpiece conveyance path for the pretreatment process toward the workpiece conveyance path for the drying process.
Herein, a conveyance path lifter mechanism is a mechanism capable of switching and connecting a lower workpiece conveyance path and an upper workpiece conveyance path, by at least one portion of a connecting workpiece conveyance path which is permitted to move up and down vertically.
In addition, when the workpiece is transferred by means of a carrier or the like from the workpiece conveyance path for the pretreatment process to the connecting workpiece conveyance path, the workpiece is displaced upward at at least one portion of the connecting workpiece conveyance path together with the carrier by means of the conveyance path lifter mechanism, whereby the carrier or the like is connected to the workpiece conveyance path for the upper drying process, and the workpiece is connected to the drying process.
In this manner, if the workpiece is displaced and transferred vertically by the conveyance path lifter mechanism of the connecting workpiece conveying path for connection, the distance between the pretreatment process and the drying process can be shortened, thus saving space.
Also, in a conveyance apparatus in which different heights are provided between a workpiece conveyance path for a pretreatment process and a workpiece conveyance path for a drying process, a connecting workpiece conveyance path is provided at an intermediate portion of the two processes. On the connecting workpiece conveyance path, a conveyance path reversing mechanism is provided to transfer a workpiece conveyed from said workpiece conveyance path for said pretreatment process toward said workpiece conveyance path for said drying process.
Herein, a conveyance path reversing mechanism is a mechanism which is capable of switching the lower workpiece conveyance path and the upper workpiece conveyance path and connecting them, by reversing at least a part of the connecting workpiece conveying path 180xc2x0.
In addition, when the workpiece is transferred by means of a carrier from the workpiece conveyance path for the pretreatment process to the connecting workpiece conveyance path, the workpiece is reversed by 180xc2x0 at at least one portion of the connecting workpiece conveyance path together with the carrier by means of the conveyance path reversing mechanism, whereby the carrier is connected to the workpiece conveyance path for the upper drying process, and the workpiece is conveyed to the drying process.
In this manner, even though the connecting workpiece conveyance path is reversed 180xc2x0 by means of the conveying path reversing mechanism of the connecting workpiece conveyance path and the workpiece is transferred, the distance between the pretreatment process and the drying process can be shortened, thus saving space.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and of the scope of the invention will become apparent to those skilled in the art from this detailed description.